1. Field of the Invention
The present invention concerns a mower comprising:                a chassis having in particular a transverse beam and two lateral uprights provided with wheels,        a connecting means allowing said chassis to be connected to a motor vehicle,        at least one harvesting mechanism provided with cutting elements,        a suspension device connecting said harvesting mechanism to the chassis, allowing a heightwise displacement of said harvesting mechanism with respect to the chassis,        a lightening device of said harvesting mechanism.        
2. Discussion of the Background
In the known mowers of this type, the lightening device is generally constituted by draw-springs arranged between the chassis and the suspension device. These springs then exert an upwards traction on the suspension device and the harvesting mechanism and thus transfer part of their weight on the chassis. This lightening prevents the harvesting mechanism from resting too heavily on the ground. It can thus easily follow the unevennesses of the ground. This reduces the risk of mistreatment of the plant cover, which could result from too strong a pressure of said mechanism on the ground. The power to be developed for moving the machine during work can also be reduced. Finally, the wear of the parts of the harvesting mechanism which rub on the ground is less rapid.
The draw-springs which are currently known are, however, voluminous and bulky, in particular when the mower has a large working width. There is also a risk of the jamming of products between the turns of these springs, which could be harmful to their operation. Finally, their cost is relatively high.
The document FR 2 786 977 describes a mower with a lightening device constituted by draw-springs fixed laterally to the chassis and indicates that these draw-springs can be replaced by torsion bars.